Current applications for mobile devices such as cell phones, and personal digital assistants make use of a user's current location. These applications may provide targeted advertisements based on a user's location (e.g., display a coupon for a coffee shop near the user's current location), or may alert the user to friends that may be nearby.
More sophisticated applications may make use of what is known as a track. A track is a set of location identifiers and temporal identifiers associated with a user. For example, a track may describe a user's commute or a favorite jogging route of the user.
However, while comparing a user's current location with sponsored locations for targeted advertising purposes, or comparing a user's current location with current locations of their friends is relatively simple, comparing tracks is more difficult. For example, because two users may walk on different sides of the street, have different speeds, or stop at one or more different locations than each other during an otherwise identical trip, the tracks describing each of their trips may be different.